Radial commutator



Oct. 17, 1939. L. SCRUGGS 2,176,361

RADIAL COMMUTATOR Filed April 15, 1957 FIGZ.

ar I an! y A TTORNE Y /WXM Patented Oct. 17, 1939 UNITED STATES PATENTOFFICE Claims.

This invention relates to commutators or small, fractional horsepowerelectric motors.

One object of my invention is to provide a commutator of the radial typethat can be manufac- 5 tured easily and at a low cost.

Another object is to provide a radial commutator for small electricmotors, which is of such design that there is no possibility of electriccurrent acting upon the plastic insulating material 1;) of which thebody part of the commutator is constructed, in such a manner as to causesaid plastic insulating material to char and thus permit the current toshort circuit or are across the segments of the commutator.

And still another object of my invention is to provide a commutator ofthe type and kind above referred to, which is of such design that it isunnecessary to wrap a binding element around the portions of thearmature wire that extend between the armature and the commutator as isnow the practice, in order to prevent said wires from being thrownoutwardly or radially by centrifugal force in the event said wires arebaggy or in a sagging condition.

Figure 1 of the drawing is a top plan view of the metal stamping that isused to form the brush-contacting portions or metal segments. of myimproved radial commutator.

Figure 2 is an edge view of said stamping after the terminal portions ofthe radially disposed arms of same have been deformed. I

Figure 3 is a plan view of the mica membe that is used to prevent theBakelite or similar plastic material from charring.

Figure 4 is a vertical transverse sectional view of the stamping afterthe radially disposed parts at the inner and outer edges of the annularportion of same have been bent upwardly so as to permit the mica memberto be preliminarily positioned upon said stamping in the operation ofcombining the mica member with the stamping.

Figure 5 is a vertical transverse sectional view of said stamping afterit has been bent so as to interlock the mica member with same and impartthe final shape to said stamping.

Figure 6 is a vertical transverse sectional View illustrating the metalstamping combined with the plastic material which constitutes the bodypart of the commutator.

Figure '7 is a side elevational view of the device shown in Figure 6.

Figure 8 is a vertical transverse sectional view of the device shown inFigure 6 after the annular portion of the stamping has been severed o todivide said annular portion into segments or brush-contacting portionsthat are separated from each other by gaps or slots.

Figure 9 is a side elevational view of the device shown in Figure 8.

Figure 10 is an enlarged end View of the com- 5 plete or finishedcommutator showing the brushcontacting portions of same in frontelevation; and

Figure 11 is an enlarged sectional view of the commutator showing itmounted on the armature 10 shaft in assembled relationship with thearmature.

My improved commutator is of the radial type and is adapted to bemounted on an armature shaft A with the brush-contacting portions or 15segments B of the commutator projecting radially from the armature shaftand disposed at right angles to same as shown in Figure 11, saidcommutator being composed of or made up of three parts, to-wit, a metalstamping preferably of 20 copper, a cylindrical body part made ofBakelite or some other suitable plastic insulating material that can bemolded, and a piece of mica interposed between the metal stamping andthe Bakelite and constructed and arranged so that it ef- 25 fectivelyprotects all portions of the Bakelite and prevents the electric currentfrom short circuiting across the gaps a: between the segments orbrush-contacting portions B of the commutator,

at any portion throughout the entire length of 30 said gaps.

The metal stamping previously referred to is formed from a flat sheet ofcopper or other suitable metal and comprises an annular portion Iprovided at its outer edge without outwardly pro- 5 jecting radiallydisposed arms 2, and provided at its inner edge with inwardly projectingradially disposed lugs 3 as shown in Figure 1. After being blanked outor cut from a flat sheet, said stamping is subjected to a deformingoperation 40 so as to cause lugs 2a on the terminal portions of the arms2 to be bent into ofi-set or angular relationship with said arms to formretaining devices which assist in securely anchoring the stamping to theBakelite body part of the com- 45 mutator. After the terminal portionsof the arms 2 have been ofi-set or deformed as above described, thestamping is subjected to another deforming operation wherein theoutwardly projecting arms 2 are bent into an upwardly and 50 outwardlyinclined position with relation to the annular portion l of thestamping, and the inwardly projecting lugs 3 are bent upwardly into aposition at right angles to the annular portion I as shown in Figure 4,thereby producing a substantially annular-shaped device provided at itsouter edge with upwardly flared portions 2 and provided at its inneredge with right angularly disposed portions 3.

The next step in the operation of manufacturing the commutator consistsin assembling a piece of mica with the deformed stamping shown in Figure4. The piece of mica that I prefer to use for this purpose consists of afiat member C of substantially annular form in general outline, providedat its inner edge with notches 4 and provided at its outer edge withnotches 5, as shown in Figure 3, said member C being preferably cut froma piece of sheet mica by a die or cutter of the exact shape or outlineof the member C. After the mica member C has been superimposed upon theannular portion I of the deformed stamping shown in Figure 4 andarranged so that the upwardly projecting lugs 3 on said stamping arepositioned in the notches 4 of the member C and the flared arms 2 of thestamping are disposed oppositely to the notches 5 in the outer edge ofthe mica member, the stamping is subjected to another deformingoperation so as to bend inwardly the flared arms 2 and cause said armsto be positioned in the notches 5 and disposed at right angles to theannular portion of the stamping as shown in Figure 5.

Thereafter, the metal stamping with the mica member C interlocked withsame, is placed in a mold or die into which a plastic insulatingmaterial is introduced so as to form a cylindrical body part D providingwith a hole 6 for the armature shaft and having securely anchored to oneend of same a metal part which comprises an annular portion I providedat its peripheral edge with a plurality of integrally right angularlydisposed spaced arms 2 embedded in said body part and having their outeredges extending flush with the peripheral edge or surface of said bodypart. The terminal ends of the arms 2 are anchored to the body part bythe deformed lugs 2a which efrectively prevent the terminal ends of saidarms 2 from springing outwardly, and the mica member C constitutes aneffective protecting element that is interposed between the insulatingmaterial of the body part D and the annular metal portion I. Byreferring to Figure 11, it will be noted that the diameter of the micamember C is the same as the diameter of the annular portion I, and isalso the same as the external diameter of the body part D, thus insuringthat the entire area of the segments or brush-contacting portions B ofthe commutator will be backed up and separated from the plasticinsulating material D by a material which has great insulatingproperties, to-wit, the mica member C. Subsequently, saw cuts are formedin the annular portion of the metal stamping so as to divide saidannular portions into a plurality of segments or brush-contactingportions B that are separated from each other by gaps or slots at asshown in Figures 8, 9 and 10. In producing the slots or gaps a: justreferred to it is essential that the saw cuts extend clear through theannular portion I of the metal stamping without, however, completelysevering the mica member C or cutting into said mica member to such anextent that the continuity of said member is destroyed, because it isabsolutely essential that a continuous or uninterrupted ring of mica bedisposed between the body part D of the commutator and the annularportion of the metal stamping that constitutes the brush-contactingportions B, in order that the gaps or slots at between saidbrush-contacting portions will be closed at their inner ends and cut offor separated from the plastic insulating material of which the body partD is formed, due to the fact that the function performed by the micamember C is to protect the body part D from the electric current andprevent said body part from charring at, or adjacent to the gaps a:between the segments B and thus permitting the current to arc acrosssaid segments. In the sawing operation above referred to, it isimmaterial if the saw cuts extend into the mica member C a slightdistance for it is almost impossible to saw completely through theannular portion l of the metal stamping without slightly scoring themica member C. The important things are, 1st, that said mica member benot completely severed in the operation of dividing the annular portionl of the metal stamping into segments, and 2nd, that the mica memberprotect the entire end face of the body part D and comprise parts whichextend over those portions of the end face of said body part which liebetween the arms 2 that are embedded in the peripheral edge of the bodypart D in flush relationship with the circular outer surface of saidbody part. Therefore, I use a relatively thick mica member C of the samediameter as the end face of the body part D, and form notches 4 and 5 inthe inner and outer edges of said mica member, as previously explained.

The integral arms 2 on the brush-contacting portions B of the commutatorare used to form extensions on said brush-contacting portions to whichthe armature wires can be conveniently attached, the terminal portionsof said armature wires, designated by the reference character w inFigure 11, being positioned in grooves 1 (see Figures 9, l0 and 11)formed in the outer surface of the arms 2, and secured in position insame by soldering or in any other suitable way. In order to reduce thetendency of the terminal portions w of the armature wires to be thrownout of the grooves l by centrifugal force when the motor is inoperation, said grooves are preferably under-cut in such a way thatcentrifugal force tends to make the terminal portions of the armaturewires cling tightly to the overhanging walls of the grooves 1 in thearms 2.

As shown in Figures 6, 8 and 11, the body part D of the commutator isprovided at its inner end or side with a recess or depression forreceiving the windings y of the armature E, thereby making itpracticable to use short sections 20 of wire between the armature andthe commutator and also providing a bridge piece 8 on the body part D ofthe commutator that can be used to support and hold the portionswof thearmature wires extending between the armature and the arms 2 on thecommutator. The bridge piece 8 is formed by a flange or enlarged portionat the inner end of the body part D of the commutator and openendedslots 1a are formed in said flange 8 as shown in Figures 9, 10 and 11 toreceive the armature wires to. The slots la, similarly to the grooves 1in the arms 2, are under-cut slightly (see Figure 10) in such adirection that centrifugal force tends to cause the armature wires w tobe held in engagement with an overhanging portion on the body part ofthe armature that effectively prevents said wires from flexing orswinging outwardly in the event they are baggy or in a saggingcondition. In small electric motors of conventional construction, thecommutator is spaced a considerable distance away 7 from the armatureand after the armature wires have been attached-to the commutator abinding element is wrapped around the'portions of the armature wiresextending between the armature and the commutator so as to prevent saidwires from being thrown outwardly by centrifugal force when the motor isin operation. With my improved commutator it is unnecessary to wrap abinding element around the sections of the armature wires that liebetween the armature and the arms 2 on the commutator, due to the factthat the bridge piece 8 on the body part D in which the armature wiresare positioned is constructed so as to effectively hold the armaturewires against outward flexing or radial movement, produced bycentrifugal force. Another desirable feature of such a structure is thatit permits the use of very short sections of wire between the armatureand the commutator due, of course, to the fact that the inner end of thebody part D of the commutator is recessed so as to receive the armaturewindings y and thus permit the commutator to be arranged in closerelationship to the armature.

A radial commutator of the construction above described can bemanufactured easily and at a low cost and it has the added advantages ofeliminating the possibility of arcing across the segments; permittingthe use of short sections of wire between the armature and commutator;and providing an efficient holding and supporting means for the armaturewires adjacent to the point where said wires are attached to thecommutator.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A commutator for fractional horsepower electric motors, provided witha cylindrical body part formed of insulating material that can bemolded, radially disposed, metal brush-contacting portions on one endface of said body part separated from each other by gaps and arranged atright angles to the armature shaft, angularly disposed extensions onsaid brush-contacting portions, embedded in and extending flush with theperipheral surface of said body part, and a mica member of the samediameter as said body part, interposed between the same and saidbrush-contacting portions to form closures for the inner ends of saidgaps, that extend throughout the entire length of said gaps.

2. A commutator for fractional horsepower electric motors, provided witha cylindrical body part formed of insulating material that can bemolded, radially disposed, metal brush-contacting portions on one endface of said body part separated from each other by gaps and arranged atright angles to the armature shaft, right angularly disposed, integralextensions on said brush-contacting portions embedded in the peripheraledge of said body part, and a mica member interposed between said bodypart and said brush-contacting portions to form closures for the innerends of said gaps, said mica member having a diameter at least equal tothat of said body part, and being provided in its peripheral edge withnotches that receive the extensions on said brush-contacting portions.

3. A commutator for fractional horsepower electric motors, provided witha cylindrical body part formed of insulating material that can bemolded, segmental-shaped brush-contacting portions on one end face ofsaid body part separated from each other by gaps and arranged at anangle to the armature shaft, a mica member of substantially annular formin general outline arranged between said segmental-shapedbrushcontacting portions and said body part and positioned so as to formclosures for said gaps that extend throughout the entire length of saidgaps, and integral angularly disposed extensions on saidbrush-contacting portions, positioned in notches in the peripheral edgeof said mica member and imbedded in the peripheral surface of said bodypart.

4. A commutator for fractional horsepower electric motors, provided witha cylindrical body part formed of insulating material that can bemolded, segmental-shaped brush-contacting portions on one end face ofsaid body part separated from each other by gaps and arranged at anangle to the armature shaft, a substantially annular shaped mica memberof the same diameter as said body part, arranged between saidsegmental-shaped brush-contacting portions and said body part andpositioned so as to form closures for said gaps that extend throughoutthe entire length of said gaps, and integral angularly disposed arms atthe outer ends of said brush-contacting portions to which the armatureWires are adapted to be attached, said arms being positioned in notchesin the outer edge of said mica member and being provided at theirterminal ends with retaining devices which are embedded in theperipheral edge of said body part.

5. A commutator for fractional horsepower electric motors, provided witha cylindrical body part formed of insulating material that can bemolded, segmental-shaped brush-contacting portions on one end face ofsaid body part separated from each other by gaps and disposed in radialrelationship with the armature shaft, laterally projecting integralextensions at the inner and outer ends of said brush-contacting portionsimbedded in the material of which said body part is made, and asubstantially annular shaped mica member interposed between saidbrush-contact ing portions and said body part and provided at its innerand outer edges with notches in which said extensions are positioned,said mica member having a diameter at least equal tothe diameter of saidbody part.

6. In a fractional horsepower electric motor, the combination of anarmature, a commutator provided with a body part, segmental-shaped,radially disposed, brush-contacting portions on said body part separatedfrom each other by gaps, and integral extensions on the outer ends ofsaid brush-contacting portions provided with undercut grooves in whichthe armature wires are positioned.

7. In a fractional horsepower electric motor, the combination of anarmature, a commutator provided with a body part, segmental-shaped,radially disposed, brush-contacting portions on said body part separatedfrom each other by gaps, integral extensions on the outer ends of saidbrush-contacting portions provided with undercut grooves in which thearmature wires are positioned, and an integral portion on said body partconstructed so as toprevent excessive radial movement of the sections ofthe armature wires extending between the armature and the commutator.

8. In a' fractional horsepower electric motor the combination of anarmature, a commutator having a body part of insulating materialprovided at one end with a recess or depression for receiving thewindings of the armature, radially disposed segmental-shapedbrush-contacting portions of metal on said body part separated from eachother by gaps and provided at their outer ends with extensions to whichthe armature wires are attached, and a bridge piece on said body partwhich receives and holds against excessive radial movement the sectionsof the armature wires extending between the armature and commutator.

9. In a fractional horsepower electric motor, the combination of anarmature, a commutator having a body part of insulating materialprovided at one end with a recess or depression for receiving thewindings of the armature, radially disposed segmental-shapedbrush-contacting portions of metal on said body part separated from eachother by gaps and provided at their outer ends with extensions to whichthe armature Wires are attached, and an integral flange at the inner endof said body part provided with under-cut slots for receiving theportions of the armature wires extending between the armature and theextensions on the brush-contacting portions to which said wires areattached.

10. A commutator for fractional horsepower electric motors, providedwith a body part of insulating material that can be molded, radiallydisposed, segmental-shaped, metal brush-contacting portions on said bodypart separated from each other by gaps and disposed at right angles tothe armature shaft, laterally projecting integral arms on the outer endsof said brushcontacting portions to which extensions of the armaturewires are attached, a mica member that separates said brush-contactingportions from said body part and forms closures for the inner ends ofthe gaps between said brush-contacting portions, and a slotted bridgepiece at the inner end of said body part that receives the armature wireextensions.

LOYD SCRUGGS.

